BRUSSELS, March 18 (Reuters) - European truck design will be transformed to make driver cabs more aerodynamic, cutting emissions and improving safety, under new rules backed by EU politicians on Tuesday.

The lawmakers also effectively delayed the lifting of a ban on allowing megatrucks, which are almost as long as medium-sized aircraft, to cross borders.

The rules have to be approved by a plenary session of the European Parliament next month, which is expected to be a formality. Tuesday's vote was in the transport committee, which is leading the debate on the draft law, and it won support from all parties.

Campaigners said it was the beginning of the end of cabins shaped like bricks, which are not aerodynamic, use more fuel and mean drivers have blind spots because of their shape, putting cyclists and pedestrians at risk. The cabs of the future could look more like the front of a high-speed train.

The vote follows the European Commission's announcement last April that it was relaxing limits on cab size to give manufacturers more space to allow a more streamlined nose.

At the time, the Commission, the EU executive, said manufacturers, such as Daimler and Ford, could improve designs immediately if they wanted to, while the European Parliament is calling for the changes to be mandatory for all new lorries in the EU by 2022.

Members of the European Parliament also want the introduction of fuel-efficiency standards for EU trucks, along the lines of those already in place for EU cars and vans.

Although plenary parliamentary approval is expected in April, the work of agreeing a legal text will be left for later in the year, when it is possible some member states will try to weaken any deal.

Meanwhile, the Parliament is asking the Commission to assess fully the impact of lifting a ban to allow cross-border use of megatrucks, also known as gigaliners, which are 25 metres long and weigh 60 tonnes. That amounts to a long delay and the Parliament has asked the Commission to report back in 2016.

The Commission in 2012 sought to ease the cross-border ban by simply reinterpreting EU law, so that gigaliners could be allowed to travel between neighbouring countries that both allowed them, such as Finland and Sweden.

But environmental campaigners led opposition, saying the measure would allow increased use of what they call monster trucks, meaning less freight on railways and more pollution.

"Today is a good day for pedestrians, cyclists, drivers, hauliers and the environment," William Todts, clean vehicles officer at Transport & Environment (T&E), said in a statement.

The European Transport Safety Council also welcomed the vote, saying better visibility would be especially important for cyclists and pedestrians in urban areas. Its data found nearly 4,300 people died in collisions involving lorries in the EU in 2011.

The European Automobile Manufacturers' Association said the flexible approach to cab dimensions could improve fuel efficiency, but said it needed a transition period to take account of the life cycle of a cab, on average 15 years.

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